1. Field of the Invention
The present invention relates to a micro-machined thin film hydrogen sensor device, and a method of making and using the same.
2. Description of the Related Art
Hydrogen gas is used in variety of applications ranging from semiconductor thin film processing to rocket fuel in the aerospace industry. The combustible nature of hydrogen however, makes its detection vitally important.
About one-half of all the sensors used to measure hazardous gases measure hydrogen. The bulk of these systems utilize as the detector element a Group VIIIB metal element (Ni, Pd, Pt) that is heated to catalytically oxidize the hydrogen, with the resulting change in heat load being the measured parameter for determination of the presence of hydrogen.
Sensors of such "hot wire" type have cross-sensitivity to other easily oxidized materials, such as alcohols and hydrocarbons. Such easily oxidized materials are common components of gases in a semiconductor-manufacturing environment, and in such application the result is frequent occurrence of false alarms.
Since the current generation of hot wire sensors require an oxidation reaction for operation, such sensors are unable to detect hydrogen when it is present in inert gas streams or environments which are not of a character to support oxidative reaction. This is a severe deficiency of such hot wire sensors and limits their applicability and utility.
It would be a significant advance in the art to provide a sensor overcoming the aforementioned deficiencies of current hot wire sensors.
Another class of sensors includes metal-insulator semiconductor (MIS) or metal-oxide- semiconductor (MOS) capacitors and field effect transistors, as well as palladium-gated diodes. In general however, these sensors are limited to detecting low concentrations of hydrogen.
Because hydrogen is used in such a wide variety of environments, it is desirable to have a sensor that will be reproducible and specific to hydrogen, even with varying concentration of background gases such as oxygen, water and other contaminants.
It is also desirable to have a solid state sensor that has no moving parts, has a response time on the order of seconds, would operate with minimum power consumption, does not require frequent calibration, and could be used in a hand-held portable instrument.
The disclosures of the foregoing references are hereby incorporated herein by reference in their entireties, together with the disclosures of the following pending United States patent applications: U.S. patent application Ser. No. 09/042,698 filed Mar. 17, 1998 in the names of Gautam Bhandari and Thomas H. Baum for "Hydrogen Sensor Utilizing Rare Earth Metal Thin Film Detection Element, now U.S. Pat. No. 6,029,500" and U.S. patent application Ser. No. 09/081,957 filed May 19, 1998 in the name of Glenn M. Tom for "Piezoelectric Quartz Crystal Hydrogen Sensor, and Hydrogen Sensing Method Utilizing Same, now U.S. Pat. No. 6,029,500."
It therefore is one object of the present invention to provide an improved hydrogen sensor.
It is another object of the invention to provide a hydrogen sensor that senses the presence of hydrogen in a reproducible and hydrogen-specific manner.
It is another object of the invention to provide a hydrogen sensor that senses the presence of hydrogen in a reproducible and hydrogen-specific manner, even with varying concentration of background gases such as oxygen, water and other contaminants.
It is yet another object of the present invention to provide a solid state hydrogen sensor that has no moving parts, has a response time on the order of seconds, operates with minimum power consumption, does not require frequent calibration, has a large dynamic detection range, and can be readily embodied as a hand-held portable instrument.
Other objects and advantages of the present invention will be more fully apparent from the ensuing disclosure and appended claims.